1. Field of the Invention
This invention relates to a lamp unit using a light emitting diode (LED) that emits short-wave light, particularly to an ultraviolet (UV) lamp unit having many short-wave LEDs mounted on a printed circuit board.
2. Description of the Related Art
A short-wave LED emits the light of short-wave range not more than 400 nm or ultraviolet rays. Such LED is used for fluorescent light emission, exciting a photocatalyst and so on. A sealed lamp or a hermetically sealed lamp may be exemplified as such short-wave LED lamp. The sealed lamp has an LED chip emitting light of short-wave range. The LED is mounted on a reflector disc of a lead frame. The disc and LED chip are sealed with a resin mold, i.e. a plastic cover or plastic lens, which is made of a transparent resin such as an epoxy resin or acrylic resin. The resin mold protects the LED chip and so on from a mechanical shock and the like. The hermetically sealed lamp has short-wave LED chips mounted on a reflector disc of a metal stem. Then, a metallic glass can is fixed on the disc by caulking. The glass can protects the LED chips and so on from a mechanical shock and the like. The glass can have an upper side made of glass so as to transmit light emitted from the LED chips. A conventional short-wave LED lamp unit has the above-mentioned short-wave LED lamps mounted in multiplicity on a printed circuit board at fixed positions. Then, it provides a required light output or luminance.
However, with respect to the conventional sealed lamp, the resin mold absorbs ultraviolet rays radiated from the short-wave LED and is degraded. Consequently, the light output is lowered and the luminance is decreased. There has not been developed yet any resin mold that is free from degradation caused by the UV rays. Therefore, the LED lamp unit constituted from the sealed lamps could be improved in view of the lifetime. On the other hand, in case of the hermetically sealed lamp, the parts such as the metal stem and glass can are expensive, thereby increasing the total costs. Then, the LED lamp unit constituted from the hermetically sealed lamp could be improved in view of the costs.
An object of the present invention is to provide a short-wave LED lamp unit that is free from a problem of degradation caused by UV ray absorption so as to prevent the light output efficiency from lowering while assuring a lifetime enough long, and that can simplify overall structure so as to decrease production costs thereof.
According to a first aspect of the invention, a short-wave light emitting diode lamp unit comprises a printed circuit board on which electronic parts are mountable. A plurality of short-wave light emitting diode chips is mounted on the printed circuit board. A housing accommodates therein the printed circuit board and the short-wave light emitting diode chips, while having a light transmitting portion provided at least at a location facing a light emission side of the short-wave light emitting diode chip. The light transmitting portion is made of a glass material having high ultraviolet ray transmittance.
According to a second aspect of the invention, a short-wave light emitting diode lamp unit comprises a housing having an opening and a printed circuit board on which electronic parts are mountable. The printed circuit board is disposed inside the housing. A plurality of short-wave light emitting diode chips is mounted on the printed circuit board so that a light emission side of the short-wave light emitting diode chip faces the opening of the housing. A light transmitting plate is attached to the opening of the housing. The light transmitting plate is made of a glass material having high ultraviolet ray transmittance.
According to a third aspect of the invention, a short-wave light emitting diode lamp unit comprises a printed circuit board on which electronic parts are mountable. A plurality of short-wave light emitting diode chips is mounted on the printed circuit board. A housing accommodates therein the printed circuit board and the short-wave light emitting diode chips. The housing is made of a glass material having high ultraviolet ray transmittance into a tube shape.
According to a third aspect of the invention, a short-wave light emitting diode lamp unit comprises a printed circuit board on which electronic parts are mountable. A plurality of short-wave light emitting diode chips is mounted on the printed circuit board. A resin mold coats the short-wave light emitting diode chip. The resin mold has high ultraviolet ray transmittance.
Further objects and advantages of the invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the invention are clearly shown.